1. Field of the Invention
The present invention relates to a method of operation of a sawmill or lumber processing facility, wherein the grading and trimming operations are combined, which permits the grader to perform the function of the trimmer operator, thus, eliminating the position of the trimmer operator.
2. Description of the Related Art
In conventional sawmills, a grader works in an area ahead of the trimmer, marking boards for grade and to indicate where on the boards a cutback is required and the ends of the board are to be cut off. A cut back is typically required if a board has excessive wane of defects near the end or ends of the board.
After grading, each board proceeds to the trimmer, and the trimmer operator moves the boards which must be cut back endwise such that the desired cut points are at the saw lines. The trimmer operator also selects the trim saws to be used on the board.
Saws are typically placed at 0 ft., 1 ft., 4 ft., 6 ft., 8 ft., 10 ft., 12 ft., 14 ft., and 16 ft., from an index line. They may extend to 18 ft., 20 ft., etc. A board to be trimmed 12 ft., will be cut by the 0 ft. and 12 ft. saws. A board to be trimmed to 9 ft. will be cut by the 1 ft. and 10 ft. saws.
A drop saw or jump saw trimmer has saws at fixed positions which are lowered (in the case of a drop saw), or raised (in the case of a jump saw), to make the cross cuts to trim the board. A xe2x80x9cmoving sawxe2x80x9d trimmer has a fixed saw at one end and a moving saw which typically strokes from 4 ft. to 16 ft. (from the fixed end).
In any of these three types of trimmer saws, boards which require cut back must be moved endwise (i.e., lengthwise) in relation to the saws to remove the desired amount.
Conventional grading and trimming operations are disclosed by Greten et al, U.S. Pat. No. 4,934,229, Greten et al, U.S. Pat. No. 5,042,341, Hellgren et al, U.S. Pat. No. 4,120,33, Rysti, U.S. Pat. No. 4,164,248, and Hellstrom et al, U.S. Pat. No. 4,023,605.
Doherty et al, U.S. Pat. No. 4,484,675, disclose a conventional board turned apparatus and method, wherein a board can be turned several times for repeated inspection of both sides of the board for more accurate grading.
However, all the above references suffer from the disadvantage that a trimmer operator is required, and since the position of a trimmer operator is difficult to fill due to, at the very least, the repetitive nature of the job, the mechanization of as much as possible of the grading and trimming operations is necessary.
The object of the present invention is to provide a method of sawmill or lumber processing operation, wherein the grader and trimmer positions are combined, so that the grader performs the function of the trimmer operator, thus, eliminating the position of the trimmer operator.
In a first embodiment of the present invention, the method of grading and trimming a board or other structure having two sides includes feeding the board to a sloped turn assembly with a first side of its two sides upright, grading the first side of the board, and if cutback is desired, moving the board in a longitudinal direction to position the board for trimming, pivoting the board using the sloped turn assembly such that the board falls onto a roll case with a second side of the two sides upright, grading the second side of the board, and if cutback is desired, moving the board in a longitudinal direction to position the board for trimming, feeding the board to a trimmer, and cutting the board.
In a second embodiment of the present invention, the sloped turn assembly is replaced with a flat transfer assembly which can turn the board onto both sides for grading. If a cutback is indicated, the roll case is raised to move the board in a longitudinal direction to a position for trimming.
In a third embodiment of the present invention, instead of moving the board lengthwise at the grading station, lasers which project laser lines across the board at various increments, are moved lengthwise along the board to designate the desired trimmer saw positions by the grader via an instrumented positioning mechanism relative to a known board position established when the board arrives at the grading station. Before the board reaches the trimmer saws, the board passes over a set of rollers which move it endwise against a moveable fence such that the board is positioned relative to the trimmer saws the same as the laser lines were positioned on the board at the grading station.